Saturday, September 18, 2010

Several news items have been swirling around the shark conservation news outlets and blogs of late - from the big picture, population view to the more drilled down, scientifically-studied behavioral aspects.

Research in the Gulf of MexicoIn the aftermath of the Gulf Oil Spill, many research organizations are studying the current and long-term effects on the marine environment. Much of those effects can be very subtle and on a microscopic level that can slowly work its way up the food chain. Similar to the pollution from methylmercury that can work its way into larger ocean fish where it can accumulate, oil and the toxic brew generated from the massive use of dispersants could end up in sharks.

Oceana, one of the larger non-profit ocean conservation organizations, is embarking on a study of sharks in the Gulf through tagging and long-term monitoring of the tagged sharks health and migratory behaviors to detect any significant changes. In addition to sharks, Oceana will be studying the impact on many of the smaller organisms - the building blocks of a marine ecosystem.

As reported in Tampa Bay Online, Oceana's chief scientist Michael Hirshfield said, "We all notice the sharks and the whales and the turtles and the seabirds when an accident like this happens. If they die, it's pretty visible. It's the worms and the little tiny things that are at the bottom of the food chain that matter a lot to the rest of the Gulf ecosystem. If they die, we're not going to notice it.''

Sea Otter Predation in Central CaliforniaOn the western coast of the United States, scientists with the California Department of Fish and Game have been recording an increase in the number of great white shark predations on sea otters along the state's Central Coast. From Pismo Beach to Monterey Bay, there has been a recorded 26 cases since August.

In most cases, these attacks are considered investigative bites and probably coming from juvenile white sharks who are in the transition process from feeding on fish to mammals (adult white sharks primarily feed on marine mammals like seals and sea lions). Not finding the sufficient taste and texture of fat that the white shark needs, it moves on. But even with an investigative nibble, that can prove fatal for the sea otter. Of the 26 reported cases, only one sea otter apparently survived.

The ten-year average for sea otter predations by white sharks is only seven in August; six in September. This year's spike could lead to a new record, surpassing 2009's annual record total of sixty-three.

Fish and Game scientists are studying the increase but a definitive reason has not been established. A mild summer with cooler ocean temperatures could be a cause - making conditions closer to shore (and closer to the sea otters) more tolerable. But it could also be indicative of an increase in the overall white shark population, as mentioned in an earlier post, which would be good for the white sharks, but poses a quandary for Fish and Game officials who are entrusted with protecting sea otter populations that have been negatively impacted from decades of overhunting and encroachment by man on their natural habitat.

The Monterey County Herald discussed the issue with Fish and Game scientist Michael Harris. "Shark attacks on otters are part of nature, Harris said, but they concern researchers who want to preserve healthy populations. 'It becomes complicated,' he said. 'They are both protected species.'"

Studying Electrical SensitivityJust a little further north along the California coast, the University of San Francisco was extolling the work of one of their own, Dr. Brandon Brown, the university's winner of the 2010 Distinguished Research Award. Dr. Brown has focused much of his recent work on the characteristics of the hydrogel in sharks and other elasmobranchs that gives these animals a type of sixth sense - the ability to detect faint electrical fields given often by other animals.

Many shark enthusiasts are familiar with this feature of a shark's hunting capability. The Ampullae de Lorenzini are the pores - a kind of five-o'clock shadow seen around the nose area of a shark - that contain the hydrogel, Dr. Brown has been studying. Through his research, one of the interesting results has been his analysis of how experienced and inexperienced sharks use the hydrogel in their hunting patterns.

According to a news release from the University's news room, "By comparing mathematical models to actual shark behavior, Brown has been able to witness sharks who use their “sixth sense” to make a beeline for the source while some, thought to be less experienced hunters, spiral in toward the source of the electrical impulses. Spiraling allows them to maintain the same orientation to the impulses as they approach, so as not to lose the scent, so to speak."

The research goes on and these amazing animals continue to fascinate us all.

Read the Tampa Bay Online article on shark research in the Gulf of Mexico.Read the Monterey County Herald article on white shark predation of sea otters. Read the USF article on Dr. Brown's research on elasmobranch's hydrogel.

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The RTSea Blog was started in 2008 and now includes over 950 entries available for media or academic background research use, including observations on a wide range of topical issues and events involving the oceans, sharks, and nature in general. After a brief break in 2012-13, there will now be more posts forthcoming.

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